•The binding mode of BHA to ctDNA is an intercalative binding.•MCR-ALS approach provides quantitative information for the interaction progress.•A specific binding mainly exists between BHA and the G–C rich region of ctDNA.•The molecular docking predicts the binding mode and sites of BHA with ctDNA.•BHA binding to DNA does not induce significantly plasmid DNA damage.

The binding properties of food antioxidant butylated hydroxyanisole (BHA) associated with calf thymus DNA (ctDNA) in physiological buffer (pH 7.4) were investigated. Experimental results based on fluorescence, UV–vis absorption, circular dichroism (CD), viscosity measurements and autodocking techniques confirmed the intercalation binding between BHA and ctDNA. The changes in Fourier transform infrared spectra of ctDNA induced by BHA suggested that BHA was more prone to bind to G–C rich region of ctDNA, which was further ascertained with the molecular docking studies. Analysis of the CD spectra indicated that this binding interaction led to a transformation from B-like DNA structure toward A-like conformation. The complexation of BHA with ctDNA was driven mainly by hydrogen bonds and hydrophobic forces. The binding constants of the BHA–ctDNA complex were calculated to be 2.03 × 104, 1.92 × 104 and 1.59 × 104 L mol−1 at 298, 304 and 310 K, respectively. Gel electrophoresis results suggested that intercalated BHA molecules did not significantly affect plasmid DNA. Moreover, the concentration profiles and the spectra for the three reaction components (BHA, ctDNA, and BHA–ctDNA complex) of the system by resolving the augmented UV–vis spectral data matrix with the use of multivariate curve resolution-alternating least squares approach provided quantitative data to estimate the progress of BHA–ctDNA interaction. This study is expected to provide new insights into the mechanism of interaction between BHA and ctDNA.